In an alternate narrative of DC Comics history during the Golden Age, Supergirl, whose Kryptonian name is Kara Zor-El, emerged as Superman's youthful cousin and ally. Conceived as an extension of the Superman mythos by creators Jerry Siegel and Joe Shuster, she first appeared in Superman #23 (July-August 1943). In her introductory story, "The Maid of Might," Kara's rocket from the doomed planet Krypton arrives on Earth years after her infant cousin Kal-El's, having been delayed in suspended animation within a surviving fragment of Argo City. Discovered by Superman amid wartime chaos, she adopts the secret identity of Linda Lee and begins training under his guidance to protect humanity while concealing her existence to avoid drawing enemy attention during World War II.
Possessing powers akin to Superman's—derived from Earth's yellow sun—Supergirl demonstrates superhuman strength, flight, invulnerability, x-ray vision, and heat vision, though her abilities are initially portrayed as slightly less developed due to her younger age and later arrival. Operating primarily from Metropolis, she undertakes covert missions against Axis spies, saboteurs, and fifth columnists, often collaborating with Superman and occasionally Lois Lane. Her costume, featuring a blue skirt variant of Superman's emblematic design, reflects the patriotic fervor of the era, with stories emphasizing themes of American resilience and the fight against tyranny.
Throughout the 1940s, Supergirl's narratives evolved to include solo adventures in backup features within Action Comics and Superman titles, portraying her as an inspirational figure for young readers, particularly girls, amid wartime rationing and societal shifts. Key developments involved her enrollment in orphanage settings to maintain secrecy, encounters with whimsical villains like the Prankster or Toyman adapted for her stories, and contributions to Allied efforts, such as thwarting invasion plots. By the late 1940s, as the war concluded, her role expanded to postwar challenges, solidifying her as a enduring symbol of hope and empowerment in the Golden Age DC Universe.